1. Field of the Invention
This invention pertains to the fields of wave transmission lines, oscillators, and amplifiers. More particularly, the invention pertains to plural, parallel connected, transistor oscillators linked by a cavity.
2. Description of the Prior Art
In microwave power combiners it is desirable to combine, efficiently and usually over a wide bandwidth, microwave energy from several sources while providing effective isolation of the sources, the combiner output, and any injection locking oscillator. Although a variety of devices and systems have been developed for this purpose, deficiencies in prior art power combiners make it impossible to fully utilize the advantages of millimeter wave and higher frequencies and the advantages of solid state oscillators such as IMPATT diodes. At very high frequencies where resonant cavities are very small, combiners using resonant cavities can accommodate only a few oscillator inputs and effective cooling is difficult. All combiners are frequency dependent, but combiners involving resonance, having relatively poor isolation, and having configurations causing reflections are particularly deficient for operation over a wide bandwidth. Problems with poor isolation and reflections can be reduced by the addition of circulator devices and turning devices, but the bulk and weight of these devices is frequently a serious disadvantage while their frequency dependence reduces bandwidth and requires returning of connected and otherwise optimized devices.
Microwave power combiners of generally cubic symmetry having six orthogonally related, rectangular waveguide arms are well-known, and it is known in such combiners to provide isolation between one or more opposing arms by disposing their cross sections in orthogonal relation. However, such a combiner, which is simply an intersection of six arms with all opposing arms so disposed, or such a combiner, which has arm pairs in a configuration similar to a magic-T, obviously has many edges and reflecting surfaces at the arm junction region. Other prior art combiners of cubic symmetry have one opposing pair of arms disposed with orthogonally related cross sections and have the cross sections of the other four arms disposed in coplanar relation with a window arrangement at the arm junction to provide isolation. This arrangement also provides many edges and reflecting surfaces. Prior art waveguide junction combiners of cubic symmetry are, therefore, believed to be undersirably frequency dependent, to provide insufficient isolation, to require circulators when used with oscillators requiring injection locking, and to undesirably effect connected devices.